Contact



Jan. 5, 1932- c. EVANS 1,839,538

CONTACT Filed NOV. 15, 1926 INVENTOR. (I /34 mm Q. 6 PM ATTORNEY Patented Jan. 5, 1932 UNITED STATES PATENT OFFICE CLARENCE '1. EVANS, OF WAUWATOSA, WISCONSIN, ASSIGNOR, BI MESNE ASSIGNMENTS, TO CUTLER-HAMMER, INC., A CORPORATION OF DELAWARE con-nor Application filed November 15, 1926. Serial K0. 148,486.

This invent-ion relates to improvements in contacts for electric switches, controllers, etc. While not limited thereto the invention is particularly applicable to contacts subjected 6 in service to severe arcing.

Heretofore contacts subjected to heavy arcing have been formed of carbon or copper and both have proven to have only relatively short life due to the efiects of the arcs broken 10 thereby and probably due in part to mechanical wear.

Thus such contacts have required frequent renewals which, neglecting consequent interruptions of service, have been troublesome and expensive. On the other hand the aforementioned materials were the only materials known to have the required properties and to be not prohibitive in cost.

Moreover such contacts have only a relatively short life even when equipped with the best available blowout devices, and the present invention has among its objects to provide a contact having a materially longer life and having also such other properties as are required for commercial success.

Another object is to provide such an improved contact formed largely of copper.

Another object is to provide such an improved contact comprising a known commercial copper alloy.

Other objects and advantages of the invention will appear.

The invention will now be described in further detail reference being had to the accompanying drawing which shows in part a conventional form of switch.

The switch illustrated comprises a stationary contact 1 and a cooperating movable contact 2, both of which may be assumed to be formed of the copper alloy aforementioned.

More specifically this alloy'comprises coper and cadmium, the percentage of cadmium eing'relatively small. In practice an alloy comprising only about one and one-tenth per cent of cadmium has been found very advarb tageous for contacts subjected to severe arc ing conditions.

Tests have shown that contacts comprising this alloy with about one and one-tenth per cent cadmium will function under severe arcing conditions about three times as long as copper contacts operating under the same conditions.

Also it has been found that this alloy which is only slightly more expensive than copper has an electrical conductivity only slightly less than copper and that such an alloy is capable of cold workin to produce the properties of a hardness an durability which distinguish the same from copper and carbon.

While perhaps the success of this alloy as a contact material may be otherwise accounted for it seems probable that it surpasses both copper and carbon under severe arcing conditions because of its hardness and high annealing temperature. Also it is perhaps possible that the greater harness and durability of such a contact as that herein disclosed will render it advantageous for general use, but

probably its advantages will only be fully realized when used under severe arcing conditions.

What I claim as new and desire to secure by Letters Patent is:

1. A contact for electric switches and the like comprising an alloy of copper and cadmium, the cadmium content of said alloy being not in excess of approximately one and one-tenth per cent.

2. A cont-act for electric switches and the like comprising an alloyv of copper and cadmium, the cadmium content of said alloy be ing about one In witness scribed my na and one tenth per cent. whereof, I have hereunto sub- CLARENCE T EVANS. 

